This invention relates generally to a chiller tank system and method for chilling liquids. More specifically, this invention relates to the containment of liquids within a tank and the method for maintaining the liquids within a specific temperature range.
Apparatus and methods for keeping liquids cool, beverages or water for example, are well known. However, the storage of liquefied gases can be problematic if the gases are corrosive or otherwise potentially hazardous. The liquefied gas must be maintained at a temperature below vaporization temperature and handled safely to avoid releases of the hazardous gas.
Generally, prior apparatus for keeping liquids below a certain temperature fall into one of two categories: cooling apparatus using a thermoelectric device for reducing the temperature of liquids and beverage cooling apparatus, beer kegs, for example, using chilled fluids flowing through pipes within the kegs or storage containers. Merckel, in U.S. Pat. No. 2,376,373 discloses a brew cooling device comprising one or more open pockets made of metal shells that are positioned within the kegs. Water or other cooling fluids are circulated through the pocket by way of inlet and outlet ducts. The pocket further comprises a flow guide insert that compels the cooling fluid to pass through the depth or length of the pocket. Stanfill in U.S. Pat. No. 4,730,463 and Murray et al. in U.S. Pat. No. 1,962,322 disclose other beverage cooling systems using chilled liquid lines for cooling the brews. The ""322 reference teaches chilling coils extending into the beverage storage tank and the ""463 reference discloses a chilled liquid line parallel to the beverage conduit lines for chilling beverages wherein the dispensing system is remote from the storage site.
The majority of the remaining patents relate to cooling apparatus using a thermoelectric device connected to a cooling or chiller probe. Moren, Pat. No. 5,544,489 reveals a dispensing apparatus for a cooled liquid using a thermally conductive probe. A thermoelectric device produces a reduced temperature on a first side and a raised temperature on a second side when a direct voltage is applied to the device. The thermally conductive probe is in direct physical contact with the first surface of the thermoelectric device. A heat sink is adjacent the second surface for dissipating heat thereby reducing the temperature. This arrangement transfers thermal energy between the thermoelectric device and the liquid to be cooled.
U.S. Pat. No. 6,131,393 to Greene discloses an apparatus for cooling of stored water. A chilling chamber is connected to a water reservoir. The water to be cooled flows through a tube within the chilling chamber. The tube is coiled about a chilling probe which is connected to a thermoelectric device. The thermally conductive probe cools the heat transfer medium (water) within the chilling chamber which in turn cools the water within the coiled tube. One end of the coiled tube is connected to a faucet for dispensing the cooled water. Yamagishi et al., U.S. Pat. No. 4,977,953 teaches a latent heat regenerating apparatus using a thermoelectric cooling element to control supercooling of latent heat regenerating material for use in air conditioners which combine a refrigeration cycle capable of both cooling and heating operations.
A cryogenic liquid level measuring apparatus and probe are taught by Samuels et al. in U.S. Pat. No. 4,020,690. The liquid level in a vessel of cryogenic liquid is determined indicated by a sensing probe. None of the above-referenced disclosures discuss or resolve the problem of maintaining a uniformly chilled liquid within a tank to avoid warm spots and the resulting vaporization of volatile liquids.
The present invention advantageously comprises a chiller tank system for containing volatile liquids at a temperature below its vaporization point and at ambient pressure. Vaporization of the volatile liquid is reduced in two ways, first by utilizing an insulated tank to maintain lower temperatures and second, by positioning a chiller barrel vertically within the tank for continued chilling of the liquid without thermal stratification that occurs in systems having coiled tubes in one area of the system. The vertically positioned chiller barrel chills the liquid uniformly throughout the tank thereby avoiding thermal stratification which, in turn, minimizes vaporization.
One preferred embodiment of a chiller tank system for containment of chilled liquids comprises a first tank and a second tank positioned within the first tank. The first tank can be spaced apart from the second tank so that insulation material can be positioned between the first and second tank. The second tank defines a chamber for receiving the liquid to be chilled. The potentially volatile liquid can comprise aqueous ammonia, sodium hypochlorite, or organic solvents. The second tank can comprise a top, preferably a domed top, and a bottom for sealing the chamber. Preferably, a refrigeration unit supplies inert refrigerant to the tank. A flexible, dual hose can circulate refrigerant between the refrigeration unit and the second tank, the dual hose comprising an inner hose within an outer hose. The outer hose is concentric to and spaced apart from the inner hose thereby creating two channels, one for transporting the refrigerant to the tank and the other for transporting the refrigerant away from the tank.
In one aspect, a straight-lined, chiller barrel is preferably positioned vertically within the chamber. The chiller barrel defines a bore and is detachably connected to the dual hose for receiving the refrigerant. The straight-lined chiller barrel extends downward into the tank through an opening in the top of the tank. Because it is vertical within the tank, the chiller barrel evenly chills the liquid within the tank thereby avoiding thermal stratification that causes vaporization by creating warm spots within the liquid. The straight-lined chiller barrel preferably has a first end portion extending outwardly through the top of the second tank and connected to a support plate. A second end portion of the chiller tank is preferably adjacent the bottom of the second tank to provide even chilling of the liquid contents of the tank. The second end portion can comprise a closed or sealed end and the first end portion defines an opening into the bore. In another preferred embodiment, the chiller barrel comprises a tube positioned concentrically within its bore so that the bottom of the tube is adjacent the second end. The top of the tube extends outwardly from the chiller barrel and is connected to the outer hose of the dual hose while the inner hose extends into the tube until it is deflected into the bore of the chiller barrel. The refrigerant is transported from the refrigeration unit through the dual hose to the chiller barrel and is circulated within the chiller barrel so that the refrigerant absorbs heat from the surrounding liquid.
Preferably the chiller tank system is vented to the atmosphere by at least one vent line extending outwardly from the top of the tank. In another aspect of this invention, the tank further comprises a metering pump, a first vent extending from the top of the system and a second vent release line between the first tank and the metering pump to avoid cavitation [vapor lock.] The top of the second tank defines an opening sealable with a lid for checking contents of the tank and removing the chiller barrel. A temperature probe can also be positioned within the chamber, the temperature probe extending outwardly from the top for readability.
In one aspect, the dual hose defines two pathways for transport of the refrigerant to and from the refrigeration unit. The inner hose defines a channel as one of the pathways and an inside wall of the outer hose defines a conduit so that the inner hose can transport refrigerant in one direction and the outer hose transports refrigerant in an opposite direction. In one preferred embodiment, the inner hose is extended through tube, preferably a suction tube, and out into the bore of the chiller barrel so that refrigerant circulates through the bore thereby providing substantially uniform temperature throughout liquid within the chiller tank. The refrigerant returns to the dual hose and refrigeration unit by means of the suction tube.
An inlet pipe transports liquid into the second tank and an outlet pipe transports chilled liquid out of the second tank. A housing facility can house the tanks and refrigeration unit minimizing exposure to escaped gases if it occurs. Preferably, the vent lines extend outside of the housing facility to the atmosphere and the inlet and outlet pipes extend outside of the housing facility.
In one embodiment, the inert refrigerant is freon. Preferably, the dual hoses are flexible hoses and the refrigeration unit and the flexible hoses are precharged with freon so that the task of recharging the refrigeration system can be accomplished easily and can be performed in the field. The refrigeration unit, flexible hoses and the chiller barrel can be integral and the chiller barrel removable from the chiller tank. When the refrigerant is consumed, it is a simple matter to remove the chiller barrel, hoses and refrigeration unit and replace them with another charged system. To prevent vaporization of the liquid it is preferably to maintain the temperatures greater than 5xc2x0 C. below boiling point of the liquid. The pressure inside the chamber can be ambient pressure.